Many persons suffer from different kidney diseases, which make them dependent on dialysis treatment. Among the different methods for dialysis, peritoneal dialysis, PD, has proven to be a robust method which may be performed by the dialysis patient at his home. During PD, dialysis fluid is passed to the abdominal cavity of the patient where it is allowed to reside for a predetermined time period to allow a removal of toxic substances and excess water from the patient/body. After the expiry of the predetermined time period, the dialysis fluid is removed from the peritoneal cavity and is replaced by fresh dialysis fluid. This is repeated for a number of cycles. There are a number of different techniques with different schemes for filling and emptying the peritoneal cavity. Common for the different techniques is that a volume on the order of liters for the average patient is replaced during each cycle and that there is a plurality of cycles.
PD performed with the aid of a cycler is called APD (Automated Peritoneal Dialysis), wherein the cycler performs the successive filling of dialysis fluid and draining of dialysis fluid.
One APD-method is CCPD (Continuous Cycling Peritoneal Dialysis), wherein 4-8 exchanges of dialysis fluid are performed during night and wherein the abdominal cavity is filled with dialysis fluid during the day. Each draining is a complete draining, i.e. the abdominal cavity is substantially empty before each new filling of dialysis fluid.
Another APD-method is NIPD (Nightly Intermittent Peritoneal Dialysis), wherein 5-10 exchanges of dialysis fluid are performed during night and wherein the abdominal cavity is empty during the day. Each draining is a complete draining, i.e. the abdominal cavity is substantially empty before each new filling of dialysis fluid.
A further APD-method is TPD (Tidal Peritoneal Dialysis), wherein 5-12 exchanges of dialysis fluid are performed during night and wherein the abdominal cavity is empty or filled with dialysis fluid during the day. An initial fill volume is instilled but only a part of this fill volume, e.g. 50-80%, is drained and replaced with each cycle.
Each APD-cycle looks in principle as disclosed in the attached FIG. 1. Each cycle thus consists of a fill period F, a dwell period Dw, and a drain period Dr. The fill period F, during which the dialysis fluid is supplied to the abdominal cavity with a fill volume VF, is characterised by a relatively high flow rate of the dialysis fluid. The dwell period Dw, during which the abdominal cavity is filled with dialysis fluid, is characterised by a slow increase in the fluid volume in the abdominal cavity. This increase is a result of the ultrafiltration, i.e. the osmotic net transport of fluid from the blood of the patient to the abdominal cavity. The drain period Dr, during which the spent dialysis fluid is drained out from the abdominal cavity, exhibits two phases, a first high flow phase characterised by a relatively high flow rate of dialysis fluid, and a second low flow phase characterised by a relatively slow flow rate of dialysis fluid. The two phases are clearly distinguished from each other at a breakpoint B.
During the first high flow phase, which could last for about 5-7 min, the flow rate is typically between 250 and 300 ml/min depending on the pressure, the type of machine, etc. During the second low flow phase, which could last for about 10-15 min, the flow rate is typically less than 50 ml/min.
This means that a relatively large portion of the dialysis fluid in the abdominal cavity has been drained out during a relatively short part of the total time of the drain period Dr. Furthermore, no significant dialysis takes place when there is only a relatively small volume of spent dialysis fluid in the abdominal cavity, i.e. during the second low flow phase. Consequently, the second low flow phase constitutes a waste of time of the total time of the PD-treatment.
A further problem with the second low flow phase is that the patient can suffer from abdominal pain during this phase. When the flow rate is low or zero no dynamic pressure drop will be present over the catheter and the drain line. Because of this, a suction pressure will be transmitted to the abdominal cavity, which means the catheter can be sucked against the walls of the abdominal cavity causing said pain.